Herman's Hermits' "I Know Why"

A couple weeks ago, I happened to hear Herman's Hermits' "I Know Why," and I realized something about the melody.  There's quite a drop for the "heart" in the line "I know deep in my heart," apparently to represent the depth mentioned in that line.  I learned the notes in the melody and discovered that between "my" (A) and "heart" (C#) there's the interval of a sixth.  The next line ("I'll always feel the same") picks up with an A note again.  Not only is that a fairly large interval, but it's the largest interval in the entire melody.  The interval between most notes is either a second or a third.  Aside from that one sixth interval, the largest is a fourth (between "at" [D#] and "me" [G#] in the first line "Ev'ry time you look at me, I know why" and - with the same melody - between "so" and "fine" in the line "Ev'ry time you look so fine, I know why").